fs: Introduce DCACHE_DONTCACHE

DCACHE_DONTCACHE indicates a dentry should not be cached on final
dput().

Also add a helper function to mark DCACHE_DONTCACHE on all dentries
pointing to a specific inode when that inode is being set I_DONTCACHE.

This facilitates dropping dentry references to inodes sooner which
require eviction to swap S_DAX mode.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

diff --git a/fs/dcache.c b/fs/dcache.c
index b280e07..0d07fb3 100644 (file)
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -647,6 +647,10 @@ static inline bool retain_dentry(struct dentry *dentry)
                if (dentry->d_op->d_delete(dentry))
                        return false;
        }
+
+       if (unlikely(dentry->d_flags & DCACHE_DONTCACHE))
+               return false;
+
        /* retain; LRU fodder */
        dentry->d_lockref.count--;
        if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST)))
@@ -656,6 +660,21 @@ static inline bool retain_dentry(struct dentry *dentry)
        return true;
 }
 
+void d_mark_dontcache(struct inode *inode)
+{
+       struct dentry *de;
+
+       spin_lock(&inode->i_lock);
+       hlist_for_each_entry(de, &inode->i_dentry, d_u.d_alias) {
+               spin_lock(&de->d_lock);
+               de->d_flags |= DCACHE_DONTCACHE;
+               spin_unlock(&de->d_lock);
+       }
+       inode->i_state |= I_DONTCACHE;
+       spin_unlock(&inode->i_lock);
+}
+EXPORT_SYMBOL(d_mark_dontcache);
+
 /*
  * Finish off a dentry we've decided to kill.
  * dentry->d_lock must be held, returns with it unlocked.

diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index fa8554b..d7deab6 100644 (file)
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -561,7 +561,7 @@ xfs_iget_cache_miss(
         */
        iflags = XFS_INEW;
        if (flags & XFS_IGET_DONTCACHE)
-               VFS_I(ip)->i_state |= I_DONTCACHE;
+               d_mark_dontcache(VFS_I(ip));
        ip->i_udquot = NULL;
        ip->i_gdquot = NULL;
        ip->i_pdquot = NULL;

diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index c1488cc..a81f0c3 100644 (file)
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -177,6 +177,8 @@ struct dentry_operations {
 
 #define DCACHE_REFERENCED              0x00000040 /* Recently used, don't discard. */
 
+#define DCACHE_DONTCACHE               0x00000080 /* Purge from memory on final dput() */
+
 #define DCACHE_CANT_MOUNT              0x00000100
 #define DCACHE_GENOCIDE                        0x00000200
 #define DCACHE_SHRINK_LIST             0x00000400

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 44bd45a..7c3e8c0 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3055,6 +3055,7 @@ static inline int generic_drop_inode(struct inode *inode)
        return !inode->i_nlink || inode_unhashed(inode) ||
                (inode->i_state & I_DONTCACHE);
 }
+extern void d_mark_dontcache(struct inode *inode);
 
 extern struct inode *ilookup5_nowait(struct super_block *sb,
                unsigned long hashval, int (*test)(struct inode *, void *),